1. Field of the Invention
This invention relates to spandex fibers that contain, for protection against discoloration by atmospheric fumes and light, a combination of N,N-dialkylsemicarbazide groups and an ultraviolet light absorber. More particularly, the invention concerns such a fiber wherein (a) the semicarbazide groups are substituents on an additive to the fiber or are end groups of the spandex polymer and (b) the light absorber is a hydroxyphenyl-1,3,5-triazine.
2. Description of the Prior Art
Spandex fibers are usually protected against discoloration and degradation by a combination of additives. Such combinations may include phenolic antioxidants, tertiary amine stabilizers, semicarbazides, pigments and the like.
Spandex fibers, especially those having polyether soft segments, usually are stabilized by phenolic antioxidants. A frequently used phenolic antioxidant, is "Cyanox" 1790, made by American Cyanamid. Susi, U.S. Pat. No. 4,619,956, discloses such antioxidants. Other frequently used phenolic stabilizers are polymeric phenols, such as those disclosed by Hunt, U.S. Pat. Nos. 3,553,290 and 3,546,173. Spandex fibers often, also contain a polymeric tertiary amine as a secondary stabilizer to further protect the spandex against discoloration and/or degradation, as well as to provide the spandex polymer with sites for acid dyes. Such polymeric amines are disclosed by Hunt, U.S. Pat. No. 3,428,711 or Bottomley and Hunt U.S. Pat. No. 3,555,115.
The stability of spandex can be improved by adding semicarbazide groups, either in the form of end groups on the spandex polymer chains, as disclosed in Research Disclosure 14428 of Apr. 10, 1976, or as an N,N-dialkylsemicarbazide additive, as disclosed by Rosendahl et al, U.S. Pat. No. 3,399,167, and by Saitoh et al, U.S. Pat. No. 4,499,221. Japanese Patent Application Publication 11948-81 discloses use of a combination of N,N-dialkylsemicarbazides and specific phenolic antioxidants and benztriazole-type ultraviolet light absorbers for stabilizing polyurethanes.
Swiss Patent 480,091 to Ciba discloses hydroxyphenyl-1,3,5-triazines as ultraviolet light stabilizers for a wide variety of polymers, including polyurethanes.
Thus, phenolic antioxidants, semicarbazide stabilizers and various ultraviolet light stabilizers are each known to help protect polyurethane polymer against discoloration and degradation. The phenolics and semicarbazides reduce discoloration of spandex exposed to combustion fumes, or to combinations of nitric oxides and ultraviolet light (referred to as "UV light"), as are often encountered in urban environments. The light stabilizers, on the other hand, generally are not known to prevent discoloration by fumes or nitric oxides. Light stabilizers usually are not of much importance in spandex polymers because the usually-used phenolic antioxidants, in themselves, provide very good protection against UV light. Also, light stabilization usually can be further enhanced by the presence of semicarbazides and/or by adding a pigment, such as titanium dioxide. Yet, with such additive combinations, spandex fibers still discolor more than "hard" (i.e., non-elastomeric) fibers, such as nylon when exposed to atmospheres containing combustion fumes or nitric oxide, especially in the presence of ultraviolet light. Also, benzotriazole light stabilizers and hindered amine stabilizers, which are generally useful in many polymers, do not improve the resistance of spandex fibers to discoloration in combustion fumes and atmospheres that contain nitrogen oxides. Sometimes, commonly used benzotriazole and hindered amine stabilizers cause undesirable side effects, such as discoloration of the spandex in water containing traces of copper, or degradation in chlorinated water.
Although the known stabilizers and many combinations thereof have been useful in improving the discoloration resistance of spandex polymers in the past, further improvements in the spandex stabilization would significantly enhance the utility of the spandex fibers, yarns and fabrics. A purpose of this invention is to provide such a stabilization improvement.